The application of hybridoma methodology to oncology has given enormous impetus to the use of novel therapeutic approaches in cancer treatment. The obvious potential of monoclonal-antibody-based treatment modalities is unfortunately limited by difficulties involved with obtaining appropriate monoclonals and with the cost of commercializing their use. As a revolutionary alternative, this proposal offers utilization of protein engineering to develop "programmable" antibody binding sites. In Phase I we will synthesize genes for VH and VL domains of a model high affinity antibody. Isolation of the expressed proteins will permit reassembly of the Fv binding site. This will be thoroughly characterized with respect to structural and binding properties. Concurrent computer analysis will subsequently permit rational design of binding sites of predetermined specificity. In later stages of this project the VH and VL genes will be altered to refashion the original Fv binding site. Furthermore, a single polypeptide binding site derived from the Fv structure will be designed by computation and executed by recombinant DNA methodology. The single gene for this binding site is ideal for fusion to the gene for a cytotoxic agent, such as ricin A subunit. We will generate such a chimeric species for trial studies in vitro.